Influence of in-vitro culture conditions and maternal metabolic status during embryonic genome activation on the Day-4 embryo transcriptome

Milk production during the early postpartum in dairy cows can impact the circulating metabolites and negatively affects embryo survival. However, the molecular consequences for the embryo during its development in the oviduct are still unknown. The objective was to determine the impact of metabolic status on embryonic genome activation (EGA) using high-throughput sequencing to generate comprehensive transcriptome profiles of bovine 16-cell stage embryos which had undergone EGA in vitro or in the oviducts of primiparous postpartum dry or postpartum lactating Holstein Friesian cows. Overall design: Two days after synchronized estrus, in vitro produced (IVP) 2- to 4-cell stage embryos were endoscopically transferred in pools of 50 into the oviduct ipsilateral to the corpus luteum of lactating (LACT, n=3) or nonlactating (i.e. dried off immediately at calving; DRY, n=3) dairy cows. On Day 4, the oviducts were flushed to recover the embryos. Pools of five Day-2 embryos (n=5) and Day 4 16-cell stage embryos obtained in vitro (n=3) or from LACT or DRY cows were subjected to RNAseq.